Environmental risk factors for Toxoplasma gondii seropositivity and its association with allostatic load in residents of central North Carolina

Toxoplasma gondii infection can be acquired through ingestion of undercooked meat or environmental oocysts excreted by cats. This cross-sectional study of 206 adults in the Durham-Chapel Hill, North Carolina metropolitan area had two objectives: 1) to assess environmental risk factors for Toxoplasma gondii infections and 2) to evaluate an association of chronic infections with biomarker-based measure of physiologic dysregulation known as allostatic load (AL). Serum samples were tested for IgG antibody to T. gondii using commercial diagnostic ELISA kits. AL was estimated as a sum of 15 biomarkers of health dichotomized at distribution-based cutoffs. Vegetated land cover within 500 m of residences was estimated using 1 m resolution data from USEPA's EnviroAtlas. Odds ratios (OR) of T. gondii seropositivity (N = 17, 8.3%) were 5.3 (95% Confidence Limits 1.4; 20.7) for handling soil with bare hands at least weekly and 10.0 (2.0; 50.6) for current cat ownership, adjusting for sociodemographic covariates and eating undercooked meat. The interaction effect of having an outdoor cat and handling soil was also statistically significant. An interquartile range (IQR) increase in distance-weighted vegetated land cover within 500 m of residence was associated with 1.7 (1.04; 2.7) OR of handling soil weekly, and, in separate analysis, with 3.7 (1.5; 9.1) OR of T. gondii seropositivity adjusting for covariates and spatial autocorrelation. Adjusted mean AL was 61% (13%; 130%) greater in seropositive individuals. Greater vegetated land cover was associated with lower AL in seronegative (p < 0.0001) and seropositive (p = 0.004) individuals. The results suggest that some individuals residing in green areas could be at a higher risk of acquiring T. gondii infections through inadvertent ingestion of soil contaminated with cat feces. These zoonotic infections may partially offset the health benefits of green spaces in a subset of the population. This abstract does not reflect EPA policy.